Drug abuse and addiction pose major health problems to individuals worldwide. The brain biology of drug addiction is thought to involve a variety of brain structures that evolved to have a role in natural rewards, such as finding food or having sex. Drugs of abuse are used in part because they make an individual "high" or euphoric when they are taken. Much of the evidence learned thus far about drug addiction suggests that regions of the brain, including the ventral tegmental area which uses the neurotransmitter dopamine, and the nucleus accumbens have a major role in reward and the experience of euphoria. Additional evidence indicates that humans reliably develop a high voltage electroencephalographic (EEG) waveform in the alpha band during the experience of euphoria. We propose to use the functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) method to study the regional changes in brain activity during the experience of euphoria in humans. Human volunteers will be screened for medical or psychiatric problems that prevent them from participating in the study. Subjects will then be given a dose of dextroamphetamine, and the ongoing activity in their brain will be studied with fMRI BOLD. Subjects will be asked to indicate when they feel euphoric, and we will use statistical analysis to determine which brain regions seem to produce the euphoria, and how they are interconnected to other brain regions. In the future, we plan to combine this method with other methods, including EEG, so that we might begin to develop a detailed understanding of the temporal and spatial changes in brain activity during the euphoric experience. Additionally, we plan to investigate how different drugs of abuse, and some medications that might interfere with the effects of drugs of abuse, affect the human reward system. Eventually, we believe that a better understanding of the brain structures that allow us to get high, and become addicted, will lead to improved awareness and treatment for substance abuse.